1. Field of the Invention
The present invention relates to a fluid control valve and fluid supply/exhaust system. In greater detail, the present invention refers to a fluid control valve, and a fluid supply/exhaust system, in which a member xe2x80x9caxe2x80x9d is made unitary with a rod shaped shaft which applies pressure to a valve holder and is moved upwardly and downwardly by a coil using electromagnetic induction, and thereby, the portion between the valve seat and the valve holder is opened and closed. The fluid control valve and fluid supply/exhaust system of the present invention is chiefly used in semiconductor manufacturing apparatuses.
2. Description of the Related Art
Conventionally, fluid control valves which controlled fluids flowing through the valve body by means of opening and closing a portion between a valve body by means of opening and closing a portion between a valve seat and a valve holder using a drive unit and valve holders comprising a diaphragm and a diaphragm holder, and were of the following types:
One type having a rotating mechanism unit which is manually operated, in which a valve rod is moved upwardly and downwardly using the rotational movement of the rotating mechanism unit, and the portion between the valve seat and the diaphragm is opened and closed (hereinbelow, this type of fluid control valve is referred to as a manual valve (not shown in the figures));
A second type having a gas filling and discharge mechanism, in which the valve rod is moved upwardly and downwardly using a difference in pressure in this gas, and the portion between the valve seat and the diaphragm is opened and closed (hereinbelow, this type of fluid control valve is referred to as an air pressure valve, (FIG. 4)); and
A third type having a mechanism which is subject to electromagnetic induction using a coil, wherein an iron core and plunger are installed at separate locations using this mechanism, and in concert with this, a bubble disc affixed to a plunger is moved upwardly and downwardly, and a portion between the bubble disk and a valve seat is opened and closed (hereinbelow, this type of fluid control valve is referred to as an electromagnetic valve (FIG. 5)).
Hereinbelow, the method of opening and closing the valve in electromagnetic valves and air pressure valves, which are referred to as automatic valves, will be explained.
FIG. 4 is a schematic cross sectional view of an air pressure valve of a type in which the open and closed state of the valve is normally closed; the state is depicted in which the valve is closed. The opening and closing operation of the value is given below.
(Closed to Open Operation)
As a result of filling an instrumentation gas input port 01 with an instrumentation gas by means of an instrumentation gas changeover switch (not shown), an actuator 402 pushes upward, and simultaneously therewith, a rod shaped valve rod 403 which is affixed to actuator 402 is pushed upward, so that the diaphragm 404, which is pushed against by valve rod 403, separates from valve seat 405, and the fluid output port 407.
(Open to Closed Operation)
As a result of ceasing the filling of the instrumentation gas input port 401 with the instrumentation gas by means of the instrumentation gas change over switch (not shown), the actuator 402, and the rod shaped valve rod 403 which is affixed to the actuator 402, are pushed downward as a result of the force of spring 408, and diaphragm 404 is pushed by valve rod 403 and diaphragm 404 comes into contact with valve 405, and the flow of the fluid from fluid input port 406 to fluid output port 407 is halted.
FIG. 5 is a schematic cross section view of an electromagnetic valve in which the valve state is normally closed; the state is depicted in which the valve is closed. The opening and closing operation of the valve is as follows.
(Closed to Open Operation)
As a result of inputting electricity from terminal 501 and causing a current flow in coil 502, electromagnetic induction is set up in coil 502, and the iron core 503 affixed to the case and plunger 504 come into contact, and along with this, the valve disk 505 which is affixed to plunger 504 is pushed upward, so that the valve disk 505 and the valve seat 506 are separated, and fluid flows from valve input port 507 to valve output port 508.
(Open to Closed Operation)
By cutting off the flow of current to coil 502, the magnetic field of coil 502 is eliminated, and the plunger 504 which was in contact with iron core 503 separates therefrom, and as a result, the valve disk 505 which was affixed to plunger 504 is pushed downward by the force of a screw 509, so that valve disk 505 and valve seat 506 come into contact, and the flow of fluid from fluid input port 507 to fluid output port 508 is stopped.
However, it has been discovered by the present inventors that these valves exhibit the following problems with respect to the response time (i.e., the amount of the time required from the state in which the valve was closed to that in which it is opened).
(1) In the case of the manually operated valve, the time required to rotate the handle is the response time, so that there are differences produced depending on the individual operators, and it is extremely difficult to stably conduct the opening and closing operation of the valve in less than, for example, 100 msec, and as the number of valves to be operated increases, it is not merely the case that the time required increases, but it is also possible to make mistakes in the order of operation and to cause counter flow and the like.
(2) The air pressure valve, which is also termed an automatic valve, has a structure which is highly airtight, and can be easily controlled so long as the fluid pressure is 10 kg/cm2 or less. However, in the air pressure valve, the time required for the charging and discharging of the gas into the drive unit occupies approximately 90 percent of the response time, so that the opening and closing operation of the valve is slow, at several tens of milliseconds, and as a result of the length of the instrumentation tube which supplies the gas, or the pressure at which the gas is supplied, the response time of the valves may differ. As a result, irregularities are produced in the operational order of the valves and the actual operating order, and there are cases in which counter flow is produced.
(3) As a method of eliminating the problems in (2) above, a method has been employed in which the length of each instrumentation tube and the gas pressure within each instrumentation tube is set to the same value.
However, in, for example, fluid control devices for semiconductor manufacturing apparatuses and the like, in those apparatuses which employ a large number of fluid control valves, electromagnetic valves and the like are employed in order to charge and discharge gas in the drive units of the air pressure valves; however, because the distances between the electromagnetic valves and the air pressure valves differ for each instrumentation tube, it is necessary to arrange the lengths of each instrumentation tube to the fluid control valve which is at the greatest distance. For this reason, storage space is required in the fluid control valve for unnecessary instrumentation tubes, and with respect to the entirety of the fluid control device, as well, it is only possible to construct a system in which the rate is determined by the fluid control valve having the longest response period.
(4) As described above, electromagnetic valves are preferentially employed in the charging and discharging of gas in the drive units of the air pressure valves. In particular, as can be understood from the structure, the valves can be rapidly opened and closed within a few milliseconds. However, as is clear from this use, the structure is such as to permit gas leakage, and furthermore, there is a large amount of dead space within the valves. For this reason, such valves are not suited for uses such as the precise control of the special gases in semiconductor manufacturing processes.
The present invention has as an object thereof to provide a fluid control valve, and a fluid supply/discharge system in which fluid can be stable controlled at a press of approximately 10 kg/cm2, the valves are high speed, having a response time of few milliseconds, and the miniaturization of the valve, and, since an instrumentation system is not required, the miniaturization of the fluid supply and exhaust system is possible, and in the case in which a system is constructed using a plurality of valves, there is little counter flow of the gas.
According to the present invention the fluid control valve in which a fluid moving through the valve body is controlled by the opening and closing of the portion between a valve seat and valve holder using a drive unit, wherein this drive unit comprises a rod shaped shaft which applies pressure via a valve holder and a valve rod, and a member xe2x80x9caxe2x80x9d which is fixed around the rod shaped shaft; the member xe2x80x9caxe2x80x9d is made from a magnetic material, and has a space between it and the shaft, and a coil provided at a position parallel to the shaft moves the member xe2x80x9caxe2x80x9d upwardly and downwardly by electromagnetic induction and makes use of a spring force to open and close a portion between the valve seat and the valve holder.
By means of these characteristics, the present invention has the following functions.
By moving the member xe2x80x9caxe2x80x9d, which is made unitary with the rod shaped shaft applying pressure via the valve holder and the valve rod, upwardly and downwardly by means of magnetic induction in the coil, and also employing a spring force, the portion between the valve seat and the valve holder is opened and closed, so that it is possible to omit the operation period involved in the charge and discharge of gas in the drive unit in the air pressure valve, and thus a fluid control valve is obtained which has a high response speed of a few milliseconds in the opening and closing of the valve.
(b) Because it is not necessary to provide the instrumentation tubes, which were necessary in the air pressure valves in order to conduct the charging and discharging of gas in the drive units, or the electromagnetic valves, which were employed in order to conduct the charging and discharging of gas in the drive unites of the air pressure valves, the problems involved in the differences in response times of the valves as a result of the pressure of the gas supplied and the length of the instrumentation tubes, the problems involved in the necessity for storage space of the unnecessary instrumentation tubes, and the problems involved in the entire fluid control apparatus in that a system could only be constructed in which the rate was limited by the fluid control valve having the longest response time, are all solved.
(c) Because member xe2x80x9caxe2x80x9d is constructed from a magnetic material, member xe2x80x9caxe2x80x9d has a saturated magnetic flux density, so that by means of the electrical field generated by the coil, it is possible to pull the member xe2x80x9caxe2x80x9d at a high rate of speed in the direction of the coil. Accordingly, the shaft which is made unitary with member xe2x80x9caxe2x80x9d can also be moved upwardly and downwardly at a high rate of speed, so that it is possible to stably conduct the opening and closing of the portion between the valve seat and the valve holder at a high rate of speed. As a result, a fluid control valve is obtained which has a small response time.
In the characteristics described above, the valve holder comprises a diaphragm and a diaphragm holder, so that the structure of the parts and contact with gas is simple, and there is little dead space, and it is possible to obtain a fluid control valve having superior gas replacement characteristics.
Furthermore, by disposing a bellows about the valve holder, it is possible to obtain a fluid control valve having superior durability in valve opening and closing.
Furthermore, by using, for member xe2x80x9caxe2x80x9d, a magnetic material comprising an iron/cobalt system alloy having a saturation magnetic flux density of 2 T (Tesla) or more, or by using, as member xe2x80x9ca2xe2x80x9d, a magnetic material comprising an iron/nickel system alloy having a saturation magnetic flux density of 2 T (tesla) or more, it is possible to greatly reduce the volume of member xe2x80x9caxe2x80x9d, so that it is possible to achieve a miniaturization of the fluid control valve.
Furthermore, in the characteristics described above, by providing a mechanism for regulating the gap G positioned between the coil and member xe2x80x9caxe2x80x9d, it is possible to improve regulation of the valve stroke.
In the characteristics above, by providing, in the space between the shaft and coil, a member xe2x80x9cbxe2x80x9d comprising a magnetic material identical to that of member xe2x80x9caxe2x80x9d, it is possible to induce the magnetic flux flowing out from one end of the coil through the member xe2x80x9cbxe2x80x9d positioned between the shaft and the coil and into the other end of the coil. As a result, it is possible to effectively employ the magnetic flux generated by the coil, so that the power with which the coil pulls member xe2x80x9caxe2x80x9d is increased, and it is possible to obtain a fluid control valve having an even smaller response time. Additionally, it is also possible to reduce the electromagnetic noise which exerts undesirable effects on the control system of the current flowing through the coil on the control system of the current flowing the coil and the like.
Furthermore, in the characteristics described above, by positioning, at a position in opposition to that of member xe2x80x9cbxe2x80x9d and thus sandwiching the coil, a member xe2x80x9ccxe2x80x9d comprising the same magnetic material as member xe2x80x9caxe2x80x9d, it is possible to induce the magnetic flux flowing out of one end of the coil through the member xe2x80x9ccxe2x80x9d positioned at the outside of the core and into the other end of the coil As a result, it is possible to effectively employ the magnetic flux generated by the coil, so that the force with which the coil pulls the member xe2x80x9caxe2x80x9d increases, and it is possible to reduce the electromagnetic noise which exerts undesirable effects on other devices external to the fluid control valve.
Furthermore, in the characteristics described above, by providing, at a position in opposition to member xe2x80x9caxe2x80x9d and sandwiching the coil, a member xe2x80x9cdxe2x80x9d comprising a magnetic material identical to that of member xe2x80x9caxe2x80x9d, the magnetic flux flowing out from one end of the coil at the side of member xe2x80x9cdxe2x80x9d is induced in the direction of the members xe2x80x9cbxe2x80x9d and xe2x80x9ccxe2x80x9d described above. On the other hand, the magnetic flux flowing out of one end of the coil at the side of member xe2x80x9caxe2x80x9d is induced through members xe2x80x9cbxe2x80x9d and xe2x80x9ccxe2x80x9d described above into the other end of the coil; however, by providing member xe2x80x9cdxe2x80x9d, the convergence of magnetic flux generated by the coil, so that the force with which the coil pulls the member xe2x80x9caxe2x80x9d is increased, and it is possible to obtain a fluid control valve having a shorter response time.
Furthermore, by constructing the coil provided in parallel to the shaft from a plurality of coils disposed in series, then by means of the electromagnetic field generated by the coils described above, it is possible to increase the force with which member xe2x80x9caxe2x80x9d is drawn in the direction of the coil at high speed, that is to say, to increase the drive force.
Additionally, by providing, between the plurality of coils arranged in series, members xe2x80x9cexe2x80x9d comprising a magnetic material identical to that of member xe2x80x9caxe2x80x9d, it is possible to make uniform that drive force described above, that is to say, the force with which the member xe2x80x9caxe2x80x9d is pulled at high speed in a direction of the coil as a result of the electric field generated by the coil, and this is preferable.
Furthermore, in the characteristics described above, the magnetic material contains 5 percent by weight of vanadium, so that the workability of the material is improved. For this reason, it is possible to construct the fluid control valve at low cost. Furthermore, when the magnetic material contains 5 weight percent or less of vanadium, then it is possible to reduce the magnetic resistance while maintaining the high saturation magnetic flux density of the magnetic material. Accordingly, the permeability of the magnetic material (saturation magnetic flux density/magnetic resistance) increases, so that it is possible to more strongly induce the magnetic field flowing out of the coil.
Furthermore, by supplying the exciting current which is supplied to the coil in a divided manner between a large initial drive current until the opening of the valve and a small maintenance current after opening which serves to maintain the open state, then it is possible to suppress the power consumed in the drive unit conducting the operation which pulls member xe2x80x9caxe2x80x9d in the direction for the coil at high speed as a result of the electric field generated by the coil described above, and it is possible to prevent damage to the coil resulting from heat.
Furthermore, after the cut off of the exciting current supplied to the coil, by again supplying the exciting current to the coil for only a short period of time after a short period of time xe2x80x9ctxe2x80x9d, the soft landing control of the valve holder is possible. That is to say, the pushing force of the spring in the direction for the valve seat is reduced, so that as a result of reducing the valves closing speed, the shock effect of the valve holder with respect to the valve seat is ameliorated, and this essentially eliminates the occurrence of damage in the valve seat or valve holder.
Furthermore, by making the structure one in which the gap G positioned between the coil and member xe2x80x9caxe2x80x9d, member xe2x80x9cbxe2x80x9d, and/or member xe2x80x9ccxe2x80x9d is filled in a freely chargeable and dischargeable manner with a magnetic fluid, it is possible to reduce the magnetic resistance of the portion of gap G corresponding to the valve stroke. As a result, it is possible to achieve a miniaturization of the drive unit which conducts the operation of pulling member xe2x80x9caxe2x80x9d in the coil direction at high speed by means of the electrical field generated by the coil described above.
Furthermore, by adopting a structure in which a resin film having a predetermined thickness is interposed between member xe2x80x9caxe2x80x9d, member xe2x80x9cbxe2x80x9d, and/or member xe2x80x9ccxe2x80x9d, it is possible to reduce the impact noise which may be generated as a result of the impact of the member xe2x80x9caxe2x80x9d into member xe2x80x9cbxe2x80x9d and/or member xe2x80x9ccxe2x80x9d end surfaces during the valve opening operation.
In the fluid supply/exhaust system of the present invention constructed using fluid control valves such as those described above, no disparities are produced in the response time as a result of individual differences in the human operators or as a result of differences in instrumentation tube length or gas pressure, and furthermore, opening and closing operations can be achieved at high speed and in a constant manner by means of electrical signals, and moreover, a fluid supply/exhaust system which is small and has high reliability is made possible.
Furthermore, the system comprises fluid control valves, a unit control apparatus which is provided with a power source, a control unit, and a plurality of drive units, a control computer which is provided in a remote central control point, and communication lines which connect the control computer with the unit control apparatus; by means of conducting operations of the fluid control valves by means of operation signals S from the control computer, a simplification of the communication lines is possible, and it is possible to rapidly and accurately control a plurality of fluid control valves miniaturization and increase in control function of the fluid supply/exhaust system is possible.
Furthermore, by means of providing an opening and closing detecting apparatus in the various fluid control valves and making the structure one in which the open or closed state is communicated to the control computer via the unit control apparatus by means of signals P from the opening and closing detecting apparatuses, it is possible to detect errors in operation resulting from external noise and errors in operation an problems present int eh fluid control valves themselves, and this is preferable.